An energy absorption apparatus or spring is known to be used on a railcar in various applications and between two masses. For example, a spring is commonly used and forms an integral part of a railroad car side bearing. A railroad car side bearing is typically disposed to opposite lateral sides of a car body between a centerpiece or bolster of a wheeled truck and an underside of a railroad car body. During movement of the railcar, the spring of each side bearing acts as an energy absorption apparatus which serves to control or restrict “hunting” and limit “rolling” movements of the railcar about a longitudinal axis.
Alternatively, an energy absorption or spring is frequently used as part of a railcar buffer assembly, railcar drawbar assembly or railcar draft gear assembly. Each of these railcar devices typically includes one or more springs for absorbing, dissipating and returning energy between adjacent ends of two railcars. As will be appreciated, an increased ability to control impacts between adjacent railcars tends to increase performance characteristics of the railcar components as well as add protection to the lading carried and shipped within the railcar.
Significantly large amounts of energy and excessive resultant dynamic impacts are developed between multiple railcars during the make-up and operation of a 100 railcar or train consist. It is well known, the spring assemblies utilized in railcar draft gears are sometimes required to operate under energy impact loads measuring well in excess of 800,000 pounds. Accordingly, the materials forming the spring assemblies must have great strength or they will readily fail under the substantial loads, and energy impacts repeatedly imparted thereto during daily operation of the railcars and under adverse temperature conditions.
It is known to equip a railroad car draft gear with compressive resilient members such as spring loaded steel elements or a series of elastomeric pads arranged in stacked relationship relative to each other. In one form, a railcar spring assembly is formed from an elongated coil spring having a cylindrically shaped column of rubber-like material extending through the central core of the steel spring. As such, the steel spring offers a first independent spring rate while the rubber-like material offers a second independent spring rate. The spring loaded steel springs, utilizing a steel on steel friction interface, however, proved ineffective in some applications because of seizing and galling problems. Those spring assemblies having a column of rubber-like material with a coil spring wound thereabout have also proven unsatisfactory since the rubber-like material, when compressed under extremely heavy loads, tends to plasticize and squeeze out between the spring coils, thus, creating other serious drawbacks and related problems. Moreover, such spring assemblies have not yielded satisfactory spring rates.
There is a continuing desire to increase the carrying capacity of railcars. Of course, increasing the capacity of railcars tends to add to the dynamic loads placed upon the draft gears and other railcar suspension components. The size constraints of the housing wherein the spring assemblies are mounted, however, limit both the number and size of elastomeric pads which can be stacked therewithin. Since such springs are limited in size they are frequently subjected to increased wear due to increases in load carrying capacities of the railcars and result in a greater need for maintenance along with higher replacement needs whereby adding to the overall cost of rail transportation. Additionally, any new spring assembly must be capable of acting and serving as a replacement for an existing spring and, thus, must be sized to fit within existing housings.
Thus, there is a continuing need and desire for a simple but strong, reliable and yet inexpensive spring assembly for a railcar which embodies the strength of steel and the numerous known benefits associated with elastomeric springs without any significant change in size.